What is the fossa ovalis?

What is the fossa ovalis?

• A. A valve in the right atrium
• B. An oval depression located on the interatrial septum, a remnant of the foramen ovale in the fetal heart
• C. Muscular projection in the left ventricle
• D. A ridge on the right atrium wall

Answer: (B)

The fossa ovalis is a shallow oval depression in the interatrial septum that marks where the foramen ovale used to be in the fetal heart. In the fetus, the foramen ovale lets blood pass from the right atrium to the left atrium, bypassing the nonworking lungs. After birth, changes in pressures cause the opening to close, leaving the fossa ovalis as a remnant. The rim around it is called the limbus fossae ovalis. It isn’t a valve, a muscular projection in the left ventricle, or a ridge on the right atrial wall—the fossa ovalis is specifically this depression on the interatrial septum reflecting the closed foramen ovale.

The fossa ovalis is a shallow oval depression in the interatrial septum that marks where the foramen ovale used to be in the fetal heart. In the fetus, the foramen ovale lets blood pass from the right atrium to the left atrium, bypassing the nonworking lungs. After birth, changes in pressures cause the opening to close, leaving the fossa ovalis as a remnant. The rim around it is called the limbus fossae ovalis. It isn’t a valve, a muscular projection in the left ventricle, or a ridge on the right atrial wall—the fossa ovalis is specifically this depression on the interatrial septum reflecting the closed foramen ovale.